In an electronic circuit having an electronic component, such as IC, mounted on a circuit board, it has been an object to release efficiently heat which the electronic component generates. It has been thus proposed to stack a heat sink on a surface of the electronic component mounted on the circuit board via a heat conducting sheet having high thermal conductivity. Accordingly, it is possible to release the heat generated by the electronic component to the side of the heat sink via the heat conducting sheet, thereby enabling to release the heat from the heat sink.
As this type of heat sink, some metallic heat sink has been commonly used, which is given with microfabrication by die-casting or machine processing and then of which surface area is increased. Meanwhile, some heat sink has been proposed, which is produced by casting metallic molten metal into a porous ceramics obtained by sintering silicon carbide (e.g., see Patent Document 1).